早期胃癌の変貌―胃癌の自然史解明の立場から

Transfiguration of Early Gastric Cancer: From a stand point of elucidating a natural history of gastric cancer

　人の胃癌がいかにして発生し，どのように発育，進展してゆくかという自然史を明らかにすることは，胃癌の診断を的確にし，治療法を確立するうえに極めて重要なことである．しかし，これには臨床上種々困難な問題が伴い解明に至っていなかった．戦後X線検査法の進歩，内視鏡診断，生検の開発，進歩と普及によって，この二十年来例外的な少数例ではあるが，これら資料の集積とreviewによるretrospectiveなfollow-upが行われ，胃癌の発生，早期胃癌から進行胃癌への進展過程などの解明にヒントを与える報告が相次ぎ^1)～23)，そのアウトラインがほぼ明らかにされてから早や十数年が経過した．

　現今，早期胃癌の診断法は確立され，発見も容易となったが，全国的な視野でみれば，実際にはまだ進行胃癌が多数を占めているのが偽らざる現状である．かかる環境にありながら，過去15年以前と比較し，早期胃癌は変貌を遂げたであろうか．この疑問に答えるために最近の十数年間の自験例に基づき，胃癌の発育進展を検討し，胃癌の自然史解明の立場から早期胃癌の変貌の様相をさぐってみた．

　Has a natural history of gastric cancer completely changed over the past decade? To answer this question seven cases of gastric cancer consisting of 5 of depressed type and 2 of elevated type followed up retrospectively and/or prospectively by UGI series, endoscopy and biopsy for at least more than three years and picked up among gastric cancer cases treated at the first department of internal medicine, Aichi Cancer Center Hospital were studied.

　Follow-up periods were from 3 years and 6 months, to 11 years and 3 months. Gastric cancers of depressed type were followed up from 5 years and 2 months to 11 years and 3 months, and all cases of this type elapsed over 5 years, and two of them eventually underwent partial gastrectomy. An early gastric cancer of m and an advanced gastric cancer of pm were demonstrated.

　A case of Ⅱc type early gastric cancer which had been followed up for 11 years and 3 months appeared a depressed type of early gastric cancer over initial 10 years and 1 month. This suggested that the lesion had grown very slowly over a long period of time. On the contrary, a period of transforming from depressed early gastric cancer into Borrmann type Ⅱ of advanced cancer through Ⅱa+Ⅱc and Ⅱa+Ⅱc advanced was only 9 months.

　Biopsy findings had remained low grade malignancy during a period of early gastric cancer over 10 years but showed a rapid progress from well differentiated tubular adenocarcinoma to poorly differentiated adenocarcinoma through moderately differentiated type during a period 9 months after becoming an advanced tumor.

　Four of 5 cases of early gastric cancer of depressed type showed a malignant cycle in their course.

　In one case a Ⅱa+Ⅱc and an atypical epithelium developed on the basis of gastritis for 5 years and 2 months, and another case in which a Ⅱa lesion of early gastric cancer developed an advanced gastric cancer of Borrmann type Ⅲ through Borrmann type Ⅱ for a relatively short period of 3 years and 6 months were also observed.

　No definite difference was observed in the course between cases treated with chemotherapy and/or immunochemotherapy, and cases without chemotherapy. It is concluded that no apparent change was observed in a natural history of early gastric cancer at present.